2-Hydroxy-3-methylanthraquinone inhibits homologous recombination repair in osteosarcoma through the MYC-CHK1-RAD51 axis.

BACKGROUND: Osteosarcoma is a malignant bone tumor that usually affects adolescents aged 15-19 y. The DNA damage response (DDR) is significantly enhanced in osteosarcoma, impairing the effect of systemic chemotherapy. Targeting the DDR process was considered a feasible strategy benefitting osteosarcoma patients. However, the clinical application of DDR inhibitors is not impressive because of their side effects. Chinese herbal medicines with high anti-tumor effects and low toxicity in the human body have gradually gained attention. 2-Hydroxy-3-methylanthraquinone (HMA), a Chinese medicine monomer found in the extract of Oldenlandia diffusa, exerts significant inhibitory effects on various tumors. However, its anti-osteosarcoma effects and defined molecular mechanisms have not been reported. METHODS: After HMA treatment, the proliferation and metastasis capacity of osteosarcoma cells was detected by CCK-8, colony formation, transwell assays and Annexin V-fluorescein isothiocyanate/propidium iodide staining. RNA-sequence, plasmid infection, RNA interference, Western blotting and immunofluorescence assay were used to investigate the molecular mechanism and effects of HMA inhibiting osteosarcoma. Rescue assay and CHIP assay was used to further verified the relationship between MYC, CHK1 and RAD51. RESULTS: HMA regulate MYC to inhibit osteosarcoma proliferation and DNA damage repair through PI3K/AKT signaling pathway. The results of RNA-seq, IHC, Western boltting etc. showed relationship between MYC, CHK1 and RAD51. Rescue assay and CHIP assay further verified HMA can impair homologous recombination repair through the MYC-CHK1-RAD51 pathway. CONCLUSION: HMA significantly inhibits osteosarcoma proliferation and homologous recombination repair through the MYC-CHK1-RAD51 pathway, which is mediated by the PI3K-AKT signaling pathway. This study investigated the exact mechanism of the anti-osteosarcoma effect of HMA and provided a potential feasible strategy for the clinical treatment of human osteosarcoma.

A superior allele of the wheat gene TaGL3.3-5B, selected in the breeding process, contributes to seed size and weight.

KEY MESSAGE: A superior allele of wheat gene TaGL3.3-5B was identified and could be used in marker-assisted breeding in wheat. Identifying the main genes which mainly regulate the yield-associated traits can significantly increase the wheat production. In this study, gene TaGL3.3 was cloned from common wheat according to the sequence of OsPPKL3. A SNP in the 8th exon of TaGL3.3-5B, T/C in coding sequence (CDS), which resulted in an amino acid change (Val/Ala), was identified between the low 1000-kernel weight (TKW) wheat Chinese Spring and the high TKW wheat Xinong 817 (817). Subsequently, association analysis in the mini-core collection (MCC) and the recombinant inbred lines (RIL) revealed that the allele TaGL3.3-5B-C (from 817) was significantly correlated with higher TKW. The high frequency of TaGL3.3-5B-C in the Chinese modern wheat cultivars indicated that it was selected positively in wheat breeding programs. The overexpression of TaGL3.3-5B-C in Arabidopsis resulted in shorter pods and longer grains than those of wild-type counterparts. Additionally, TaGL3.3 expressed a tissue-specific pattern in wheat as revealed by qRT-PCR. We also found that 817 showed higher expression of TaGL3.3 than that in Chinese Spring (CS) during the seed development. These results demonstrate that TaGL3.3 plays an important role in the formation of seed size and weight. Allele TaGL3.3-5B-C is associated with larger and heavier grains that are beneficial to wheat yield improvement.

Quercetin encapsulated in folic acid-modified liposomes is therapeutic against osteosarcoma by non-covalent binding to the JH2 domain of JAK2 Via the JAK2-STAT3-PDL1.

Osteosarcoma (OS) is a malignant solid tumor prone to lung metastasis that occurs in adolescents aged 15-19 years. Neoadjuvant chemotherapy and surgical treatment aimed at curing OS have gained limited progress over the last 30 years. Exploring new effective second-line therapies for OS patients is a serious challenge for researchers. Quercetin, a multiple biologically active polyphenolic flavonoid, has been used in tumor therapy. However, the exact mechanism of quercetin is still unknown, which limits the application of quercetin. In the current study, we found that quercetin could inhibit JAK2 through the JH2 domain in a non-covalent manner, resulting in the inhibition of OS proliferation and immune escape via the JAK2-STAT3-PD-L1 signaling axis. More importantly, to overcome the shortcomings of quercetin, including low water solubility and low oral availability, we encapsulated it with folic acid-modified liposomes. The transportation of quercetin by folic acid-modified liposomes may provide a feasible strategy to cure OS.

FoxO1a mediated cadmium-induced annulus fibrosus cells apoptosis contributes to intervertebral disc degeneration in smoking.

Cadmium (Cd), a type of heavy metal that accumulates in the body because of smoking, mediates the toxic effect of smoking in many diseases, such as cardiovascular disease, osteoarthritis, and osteoporosis. However, the toxic effect of Cd on intervertebral disc tissues have not been reported. In the current study, we demonstrated that Cd induced the apoptosis of annulus fibrosus (AF) cells, which contributed to intervertebral disc degeneration (IVDD). Specifically, Cd induced the nuclear translocation of FoxO1a, which drives AF cells apoptosis through mitochondrial-related pathway. Phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signal pathway is also involved in this process. The combined use of LY29002, an inhibitor of PI3K, and small interfering RNA-targeting FoxO1a confirmed the relationship between the PI3K/AKT signal pathway and FoxO1a. In summary, present research explores the mechanism behind the contribution of smoking to IVDD and finds a new feasible target for preventing IVDD in smoking.

Identification of the WUSCHEL-Related Homeobox (WOX) Gene Family, and Interaction and Functional Analysis of TaWOX9 and TaWUS in Wheat.

The WUSCHEL-related homeobox (WOX) is a family of plant-specific transcription factors, with important functions, such as regulating the dynamic balance of division and differentiation of plant stem cells and plant organ development. We identified 14 distinct TaWOX genes in the wheat (Triticum aestivum L.) genome, based on a genome-wide scan approach. All of the genes under evaluation had positional homoeologs on subgenomes A, B and D except TaWUS and TaWOX14. Both TaWOX14a and TaWOX14d had a paralogous copy on the same genome due to tandem duplication events. A phylogenetic analysis revealed that TaWOX genes could be divided into three groups. We performed functional characterization of TaWOX genes based on the evolutionary relationships among the WOX gene families of wheat, rice (Oryza sativa L.), and Arabidopsis. An overexpression analysis of TaWUS in Arabidopsis revealed that it affected the development of outer floral whorl organs. The overexpression analysis of TaWOX9 in Arabidopsis revealed that it promoted the root development. In addition, we identified some interaction between the TaWUS and TaWOX9 proteins by screening wheat cDNA expression libraries, which informed directions for further research to determine the functions of TaWUS and TaWOX9. This study represents the first comprehensive data on members of the WOX gene family in wheat.

Rapid and Superior Bacteria Killing of Carbon Quantum Dots/ZnO Decorated Injectable Folic Acid-Conjugated PDA Hydrogel through Dual-Light Triggered ROS and Membrane Permeability.

One of the most difficult challenges in the biomedical field is bacterial infection, which causes tremendous harm to human health. In this work, an injectable hydrogel is synthesized through rapid assembly of dopamine (DA) and folic acid (FA) cross-linked by transition metal ions (TMIs, i.e., Zn2+ ), which was named as DFT-hydrogel. Both the two carboxyl groups in the FA molecule and catechol in polydopamine (PDA) easily chelates Zn2+ to form metal-ligand coordination, thereby allowing this injectable hydrogel to match the shapes of wounds. In addition, PDA in the hydrogel coated around carbon quantum dot-decorated ZnO (C/ZnO) nanoparticles (NPs) to rapidly generate reactive oxygen species (ROS) and heat under illumination with 660 and 808 nm light, endows this hybrid hydrogel with great antibacterial efficacy against Staphylococcus aureus (S. aureus, typical Gram-positive bacteria) and Escherichia coli (E. coli, typical Gram-negative bacteria). The antibacterial efficacy of the prepared DFT-C/ZnO-hydrogel against S. aureus and E. coli under dual-light irradiation is 99.9%. Importantly, the hydrogels release zinc ions over 12 days, resulting in a sustained antimicrobial effect and promoted fibroblast growth. Thus, this hybrid hydrogel exhibits great potential for the reconstruction of bacteria-infected tissues, especially exposed wounds.

Clinical Prognostic Significance of HOXC9 Expression in Patients with Colorectal Cancer.

BACKGROUND: Colorectal cancer (CRC) involves the abnormal expression of a set of genetic and epigenetic genes, which may be useful for predicting prognosis. The transcription factor homeobox C9 (HOXC9) is a member of the homeobox family and participates in diverse cellular metabolic processes. In the current study, the prognostic value of HOXC9 in CRC was evaluated by analyzing public data from The Cancer Genome Atlas. METHODS: The correlation between clinical features and HOXC9 expression levels was evaluated by logistic regression. Kaplan-Meier and Cox regression was performed to determine the association between HOXC9 expression and patient prognosis. Gene set enrichment analysis was conducted to explore the function of HOXC9 in CRC. RESULTS: HOXC9 showed higher expression in tumor tissue than in normal tissue. An increased level of HOXC9 in CRC was notably associated with an advanced tumor stage (OR = 1.58, for stage I/II vs. stage III/IV, p = 0.037), increased risk of distant metastasis (odds ratio = 1.84, for T1/T2 vs. T3/T4, p = 0.025), and tendency for venous invasion (OR = 2.25, p = 0.003). Kaplan-Meier analysis revealed that higher HOXC9 levels were predictive of poor overall (p = 0.0083) and progression-free survival (p = 0.0014). Multivariate COX regression model analysis proved that HOXC9 was independently associated with overall survival (hazard ratio = 2.88, 95% confidence interval: 1.14 - 7.29, p = 0.025). Gene set enrichment analysis showed that several biological function symbols were particularly enriched in the increased HOXC9 phenotype. CONCLUSIONS: HOXC9 may play a critical role in CRC progression and serve as a novel potential marker of poor prognosis in CRC.

H2O2 Damages the Stemness of Rat Bone Marrow-Derived Mesenchymal Stem Cells: Developing a "Stemness Loss" Model.

BACKGROUND The number of patients with spinal cord injury caused by motor vehicle accidents, violent injuries, and other types of trauma increases year by year, and bone marrow mesenchymal stem cell (BMSC) transplants are being widely investigated to treat this condition. However, the success rate of BMSCs transplants is relatively low due to the presence of oxidative stress in the new microenvironment. Our main goals in the present study were to evaluate the damaging effects of H2O2 on BMSCs and to develop a model of "stemness loss" using rat BMSCs. MATERIAL AND METHODS Bone marrow-derived mesenchymal stem cells were obtained from the bone marrow of young rats reared under sterile conditions. The stem cells were used after 2 passages following phenotypic identification. BMSCs were divided into 4 groups to evaluate the damaging effects of H2O2: A. blank control; B. 100 uM H2O2; C. 200 uM H2O2 and D. 300 uM H2O2. The ability of the BMSCs to differentiate into 3 cell lineages and their colony formation and migration capacities were analyzed by gene expression, colony formation, and scratch assays. RESULTS The cells we obtained complied with international stem cell standards demonstrated by their ability to differentiate into 3 cell lineages. We found that 200-300 uM H2O2 had a significant effect on the biological behavior of BMSCs, including their ability to differentiate into 3 cell lineages, the expression of stemness-related proteins, and their migration and colony formation capacities. CONCLUSIONS H2O2 can damage the stemness ability of BMSCs at a concentration of 200-300 uM.

MiR-20a, a novel promising biomarker to predict prognosis in human cancer: a meta-analysis.

BACKGROUND: Recently, microRNA-20a (miR-20a) has been reported to influence the clinical features and may have prognostic value in human cancers. The present meta-analysis assessed the prognostic role of miR-20a in various carcinomas. METHODS: Literature searches of seven electronic databases were performed for eligible articles of the prognostic role of miR-20a in human cancers. Hazard ratios (HR) for overall survival (OS), disease free survival (DFS), progression-free survival (PFS) as well as their 95% confidence intervals (95%CIs) were used to assess the influence of miR-20a expression on patient prognosis. Odds ratio (OR) and 95%CIs were applied to evaluate the correlation between miR-20a expression and clinicopathological characteristics. RESULTS: Based on the OS analyzed by log rank tests, there was a significant association between miR-20a levels and OS by fixed effects model. By subgroup analyses, the significance was also observed in the studies of specimen derived from blood and gastrointestinal cancer group. The independent prognostic role of miR-20a expression for the OS was observed significantly by fixed effects model. In addition, we observed significant association between miR-20a expression levels and DFS of log rank tests, DFS of cox regression. Significant relation of gender/differentiation and the expression level of miR-20a was identified. CONCLUSIONS: Base on the findings, the elevated miR-20a expression level is related to poor prognosis of gastrointestinal cancer patients. As for other types of carcinomas, the results are still not stable and more studies are required to further identify miR-20a prognostic values. In addition, miR-20a expression level is relatively higher in women than that in men, and increased miR-20a expression level is linked to poor tumor differentiation.

Corrigendum to "Cellular senescence-driven transcriptional reprogramming of the MAFB/NOTCH3 axis activates the PI3K/AKT pathway and promotes osteosarcoma progression" [Genes & Diseases 11 (2024) 952-963].

[This corrects the article DOI: 10.1016/j.gendis.2023.02.028.].

Cellular senescence-driven transcriptional reprogramming of the MAFB/NOTCH3 axis activates the PI3K/AKT pathway and promotes osteosarcoma progression.

Osteosarcoma is the most common primary malignancy of bones and primarily occurs in adolescents and young adults. However, a second smaller peak of osteosarcoma incidence was reported in the elderly aged more than 60. Elderly patients with osteosarcoma exhibit different characteristics compared to young patients, which usually results in a poor prognosis. The mechanism underlying osteosarcoma development in elderly patients is intriguing and of significant value in clinical applications. Senescent cells can accelerate tumor progression by metabolic reprogramming. Recent research has shown that methylmalonic acid (MMA) was significantly up-regulated in the serum of older individuals and played a central role in the development of aggressive characteristics. We found that the significant accumulation of MMA in elderly patients imparted proliferative potential to osteosarcoma cells. The expression of MAFB was excessively up-regulated in osteosarcoma specimens and was further enhanced in response to MMA accumulation as the patient aged. Specifically, we first confirmed a novel molecular mechanism between cellular senescence and cancer, in which the MMA-driven transcriptional reprogramming of the MAFB-NOTCH3 axis accelerated osteosarcoma progression via the activation of PI3K-AKT pathways. Moreover, the down-regulation of the MAFB-NOTCH3 axis increased the sensitivity and effect of AKT inhibitors in osteosarcoma through significant inhibition of AKT phosphorylation. In conclusion, we confirmed that MAFB is a novel age-dependent biomarker for osteosarcoma, and targeting the MAFB-NOTCH3 axis in combination with AKT inhibition can serve as a novel therapeutic strategy for elderly patients with osteosarcoma in experimental and clinical trials.

Management of pain in patients with bone metastases.

Cancer-induced bone pain (CIBP) has a considerable impact on patients' quality of life as well as physical and mental health. At present, patients with CIBP are managed according to the three-step analgesic therapy algorithm proposed by the World Health Organization. Opioids are commonly used as the first-line treatment for moderate-to-severe cancer pain but are limited due to addiction, nausea, vomiting and other gastrointestinal side effects. Moreover, opioids have a limited analgesic effect in some patients. In order to optimize the management of CIBP, we must first identify the underlying mechanisms. In some patients, surgery, or surgery combined with radiotherapy or radiofrequency ablation is the first step in the management of CIBP. Various clinical studies have shown that anti-nerve growth factor (NGF) antibodies, bisphosphonates, or RANKL inhibitors can reduce the incidence and improve the management of cancer pain. Herein, we review the mechanisms of cancer pain and potential therapeutic strategies to provide insights for optimizing the management of CIBP.

SGLT2 inhibitor activates the STING/IRF3/IFN-ß pathway and induces immune infiltration in osteosarcoma.

SGLT2 (sodium-glucose cotransporter 2) is an important mediator of epithelial glucose transport and has been reported that SGLT2, robustly and diffusely expressed in malignant cancer cells, was overexpressed in various tumors, and inhibiting the SGLT2 expression significantly inhibited tumor progression. By blocking the functional activity of SGLT2, SGLT2 inhibitors have shown anticancer effects in several malignant cancers, including breast cancer, cervical cancer, hepatocellular cancer, prostate cancer, and lung cancer. However, the anticancer effect of SGLT2 inhibitors in osteosarcoma and the specific mechanism are still unclear. In the present study, we found that SGLT2 was overexpressed at the protein level in osteosarcoma. Furthermore, our results showed that the SGLT2 inhibitor significantly inhibited osteosarcoma tumor growth and induced infiltration of immune cells in vivo by upregulating STING expression and activating the IRF3/IFN-ß pathway, which could attribute to the suppression of AKT phosphorylation. In addition, the combined treatment with SGLT2 inhibitor and STING agonist 2'3'-cGAMP exerted synergistic antitumor effects in osteosarcoma. Furthermore, the overexpression of SGLT2 at the protein level was correlated with the degradation of SGLT2 induced by TRIM21. This result demonstrated that SGLT2 is a novel therapeutic target of osteosarcoma, and that the SGLT2 inhibitor, especially in combination with 2'3'-cGAMP, is a potential therapeutic drug.

Engineered exosome as targeted lncRNA MEG3 delivery vehicles for osteosarcoma therapy.

Exosomes as nanosized membrane vesicles, could targeted deliver therapeutic agents by modification with target ligands. Exosome-derived non-coding RNAs play a vital role in the development of tumors. Previous evidences reveal that long non-coding RNA maternally expressed gene 3 (lncRNA MEG3) has anti-tumor properties. Whereas, the inhibitory effects of exosome-derived lncRNA MEG3 in osteosarcoma (OS) remain largely unknown. In this study, we utilize the engineering technology to combine exosome and lncRNA for tumor-targeting therapy of OS. We elucidated the anti-OS effects of lncRNA MEG3, and then prepared the c(RGDyK)-modified and MEG3-loaded exosomes (cRGD-Exo-MEG3). The engineered exosomes cRGD-Exo-MEG3 could deliver more efficiently to OS cells both in vitro and in vivo. In this way, cRGD-Exo-MEG3 facilitate the anti-OS effects of MEG3 significantly, with the help of enhanced tumor-targeting therapy. This study elucidates that engineered exosomes as targeted lncRNA MEG3 delivery vehicles have potentially therapeutic effects for OS.

Three-dimensional-printed titanium prostheses with bone trabeculae enable mechanical-biological reconstruction after resection of bone tumours.

Reconstruction after resection has always been an urgent problem in the treatment of bone tumours. There are many methods that can be used to reconstruct bone defects; however, there are also many complications, and it is difficult to develop a safe and effective reconstruction plan for the treatment of bone tumours. With the rapid development of digital orthopaedics, three-dimensional printing technology can solve this problem. The three-dimensional printing of personalised prostheses has many advantages. It can be used to print complex structures that are difficult to fabricate using traditional processes and overcome the problems of stress shielding and low biological activity of conventional prostheses. In this study, 12 patients with bone tumours were selected as research subjects, and based on individualised reverse-engineering design technology, a three-dimensional model of each prosthesis was designed and installed using medical image data. Ti6Al4V was used as the raw material to prepare the prostheses, which were used to repair bone defects after surgical resection. The operation time was 266.43 ± 21.08 minutes (range 180-390 minutes), and intraoperative blood loss was 857.26 ± 84.28 mL (range 800-2500 mL). One patient had delayed wound healing after surgery, but all patients survived without local tumour recurrence, and no tumour metastasis was found. No aseptic loosening or structural fracture of the prosthesis, and no non-mechanical prosthesis failure caused by infection, tumour recurrence, or progression was observed. The Musculo-Skeletal Tumour Society (MSTS) score of limb function was 22.53 ± 2.09 (range 16-26), and ten of the 12 patients scored ≥ 20 and were able to function normally. The results showed that three-dimensional printed prostheses with an individualised design can achieve satisfactory short-term clinical efficacy in the reconstruction of large bone defects after bone tumour resection.

Targeted Delivery of PD-L1-Derived Phosphorylation-Mimicking Peptides by Engineered Biomimetic Nanovesicles to Enhance Osteosarcoma Treatment.

Osteosarcoma is a rare malignant bone-originating tumor that usually occurs in young people. Programmed cell death 1 ligand 1 (PD-L1), an immune checkpoint protein, is highly expressed in osteosarcoma tissues. Several recent studies have indicated that the tumor-related role of PD-L1 in tumors, especially non-plasma membrane (NPM)-localized PD-L1, is not limited to immune regulation in osteosarcoma. Here, mass spectrometry analysis is combined with RNA-seq examination to identify the intracellular binding partners of PD-L1 and elucidate the underlying mechanism of its action. It is found that the NPM-localized PD-L1 interacted with Insulin-like growth factor binding protein-3 (IGFBP3) to promote osteosarcoma tumor growth by activating mTOR signaling. This interaction is enforced after phosphoglyceratekinase1 (PGK1)-mediated PD-L1 phosphorylation. Based on these findings, a phosphorylation-mimicking peptide is designed from PD-L1 and it is encapsulated with a Cyclic RGD (cRGD)-modified red blood cell membrane (RBCM) vesicle (Peptide@cRGD-M). The Peptide@cRGD-M precisely delivers the PD-L1-derived phosphorylation-mimicking peptide into osteosarcoma lesions and significantly promotes its therapeutic effect on the tumor. Therefore, this investigation not only highlights the function of NPM-localized PD-L1, but also uses an engineering approach to synthesize a small molecular peptide capable of inhibiting osteosarcoma growth.

LncCCAT1 interaction protein PKM2 upregulates SREBP2 phosphorylation to promote osteosarcoma tumorigenesis by enhancing the Warburg effect and lipogenesis.

Pyruvate kinase M2 (PKM2) plays an important role in the consumption of glucose and the production of lactic acid, the striking feature of cancer metabolism. The association of PKM2 with osteosarcoma (OS) has been reported but its role in OS has yet to be elucidated. To study this, PKM2­bound RNAs in HeLa cells, a type of cancer cells widely used in the study of molecular function and mechanism, were obtained. Peak calling analysis revealed that PKM2 binds to long noncoding RNAs (lncRNAs), which are associated with cancer pathogenesis and development. Validation of the PKM2­lncRNA interaction in the human OS cell line revealed that lncRNA colon cancer associated transcript­1 (lncCCAT1) interacted with PKM2, which upregulated the phosphorylation of sterol regulatory element­binding protein 2 (SREBP2). These factors promoted the Warburg effect, lipogenesis, and OS cell growth. PKM2 appears to be a key regulator in OS by binding to lncCCAT1. This further extends the biological functions of PKM2 in tumorigenesis and makes it a novel potential therapeutic for OS.

Drp1-mediated mitochondrial fission is involved in oxidized low-density lipoprotein-induced AF cella poptosis.

This study aimed to assess the negative effect of oxidized low-density lipoprotein (oxLDL) on annulus fibrosus (AF) cells and decipher the mechanism of action of the process. After treating AF cells with various concentrations (0, 25, 50, 100, and 200 µg/mL) of oxLDL for 24 and 48 hours, their viability was evaluated using cell counting kit-8 and live/dead staining. The percentage of AF cell death was determined with Annexin V/propidium iodide apoptosis staining. The expression of proteins related to the mitochondrial apoptosis pathway was determined using Western blot. Additionally, mitochondrial membrane potential (MMP) and intracellular reactive oxygen species (ROS) were assessed with JC-1 staining and dichlorodihydrofluorescein diacetate ormitoSOX probes, respectively. Mitochondrial morphology was observed with a transmission electron microscope. After treatment with oxLDL, AF cell viability decreased, pro-apoptosis proteins (such as Bax, cleaved caspase-9, and cleaved caspase-3) increased, and anti-apoptosis proteins (Bcl-2) declined. Excessive ROS and diminished MMP were also detected during this process, as were enhanced mitochondrial fission and augmented Drp1 expression. Furthermore, knocking down the expression of Drp1 rescued oxLDL-induced AF cell death. Collectively, these results suggest that oxLDL induces AF cell death through a mitochondria-related pathway. Enhanced mitochondrial fission was involved in oxLDL-induced AF cell death. Targeting Drp1, a target for regulating the process of mitochondrial fission, may be a feasible strategy for preventing intervertebral disc degeneration in hyperlipidemia.

Exosomes as Efficient Nanocarriers in Osteosarcoma: Biological Functions and Potential Clinical Applications.

Osteosarcoma is the most common bone tumor affecting both adolescents and children. Although localized osteosarcoma has an overall survival of >70% in the clinic, metastatic, refractory, and recurrent osteosarcoma have poorer survival rates. Exosomes are extracellular vesicles released by cells and originally thought to be a way for cells to discard unwanted products. Currently, exosomes have been reported to be involved in intercellular cross-talk and induce changes in cellular behavior by transferring cargoes (proteins, DNA, RNA, and lipids) between cells. Exosomes regulate osteosarcoma progression, and processes such as tumorigenesis, proliferation, metastasis, angiogenesis, immune evasion, and drug resistance. Increasing evidences shows that exosomes have significant potential in promoting osteosarcoma progression and development. In this review, we describe the current research status of exosomes in osteosarcoma, focusing on the biological functions of osteosarcoma exosomes as well as their application in osteosarcoma as diagnostic biomarkers and therapeutic targets.

FGD1 promotes tumor progression and regulates tumor immune response in osteosarcoma via inhibiting PTEN activity.

Rationale: Mesenchymal cell-derived osteosarcoma is a rare malignant bone tumor affecting children and adolescents. PTEN down-regulation or function-loss mutation is associated with the aggressive of osteosarcoma. Explicating the regulatory mechanism of PTEN might highlight new targets for improving the survival rate of osteosarcoma patients. Methods: The clinical relevance of FGD1 was examined by the TCGA data set, Western blotting and immunohistochemistry of osteosarcoma microarray slides. Functional assays, such as the MTS assay, colony formation assay and xenografts, were used to determine the biological role of FGD1 in osteosarcoma. The protein-protein interaction between FGD1 and PTEN was detected via co-immunoprecipitation. The relationship between FGD1 and PD-L1 was examined by Western blot analysis, RT-qPCR and immunohistochemistry. Results: In this study, analysis of the TCGA data set of sarcomas revealed that FGD1 was over-expressed with the highest P values. Then, we demonstrated that FGD1 was also abnormally up-regulated in osteosarcoma with unfavorable prognosis. Aberrant expressed FGD1 promoted the osteosarcoma tumor cell proliferation and invasion. Moreover, we found that FGD1 was participated in activating PI3K/AKT signaling pathway by interacting with PTEN. Finally, we showed that FGD1 was capable of regulating the tumor immune response via the PTEN/PD-L1 axis in osteosarcoma. Conclusions: Our data suggested that abnormally over-expressed FGD1 functions as an oncogenic protein to promote osteosarcoma progression through inhibiting PTEN activity and activating PI3K/AKT signaling. Notably, FGD1 increased PD-L1 expression in a PTEN dependent manner and modulated the sensitivity of immune checkpoint-based immunotherapy in osteosarcoma. Thus, FGD1 might be a potential target for improving the survival rate of osteosarcomas.